Assessment of right atrial pressure-volume relations in patients with and without an atrial septal defect.

Assessment of the complex relations between pressure and volume in the right atrium has been hampered in the past by difficulties in the measurement of atrial volume. Accordingly, in the present study the dynamics of right atrial pressure-volume relations were examined (with the use of an impedance catheter to measure right atrial volume) in patients with and without an atrial septal defect. Right atrial pressure and impedance volume were measured in 16 patients at the time of cardiac catheterization with the use of a multi-electrode impedance catheter to provide continuous, on-line, pressure-volume data. Eleven patients without evidence of an interatrial shunt were examined during normal respiration and during the Valsalva maneuver and contrasted with five patients with an atrial septal defect documented by oxygen saturation step-up and echocardiographic studies. Right atrial pressure-volume diagrams in patients without an atrial septal defect exhibited the normal figure eight pattern, with an A loop (atrial contraction) and a V loop (passive filling), corresponding to the A wave and V wave of right atrial pressure, respectively. During inspiration, mean right atrial pressure decreased and mean right atrial volume increased, consistent with augmented venous return. With the Valsalva maneuver, right atrial pressure increased and both right atrial stroke volume and mean right atrial volume decreased compared with baseline. Patients with an atrial septal defect demonstrated baseline pressure-volume diagrams similar to those of patients without an interatrial shunt. However, no change in mean right atrial volume occurred with either respiration or the Valsalva maneuver despite changes in right atrial pressure similar to those seen inpatients without an atrial septal defect.(ABSTRACT TRUNCATED AT 250 WORDS)